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Association between Haemagglutination inhibiting antibodies and protection against clade 6B viruses in 2013 and 2015

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  • Association between Haemagglutination inhibiting antibodies and protection against clade 6B viruses in 2013 and 2015

    Vaccine. 2017 Oct 3. pii: S0264-410X(17)31265-3. doi: 10.1016/j.vaccine.2017.09.036. [Epub ahead of print]
    Association between Haemagglutination inhibiting antibodies and protection against clade 6B viruses in 2013 and 2015.

    Ng S1, Saborio S2, Kuan G3, Gresh L4, Sanchez N4, Ojeda S4, Harris E5, Balmaseda A2, Gordon A6.
    Author information

    Abstract

    BACKGROUND:

    The epidemiology of the pandemic A(H1N1) virus has been changing as population immunity continues to co-evolve with the virus. The impact of genetic changes in the virus on human's susceptibility is an outstanding important question in vaccine design. In a community-based study, we aim to (1) determine the genetic characteristics of 2009-2015 pandemic H1N1 viruses, (2) assess antibody response following natural infections and (3) assess the correlation of A/California/07/09 antibody titers to protection in the 2013 and 2015 epidemics.
    METHODS:

    In a household transmission study, serum specimens from 253 individuals in Managua, Nicaragua were analyzed. Combined nose and throat swabs were collected to detect RT-PCR confirmed influenza infection and virus sequencing. Hemagglutination inhibition assays were performed and the protective titer for circulating H1N1pdm was determined.
    RESULTS:

    Clade 6B pandemic H1N1 viruses predominated in Nicaragua during the 2013 and 2015 seasons. Our household transmission study detected a household secondary attack rate of 17% in 2013 and 33% in 2015. Infected individuals, including vaccinees, showed an apparent antibody response to A/California/07/09. Baseline titers of A/California/07/09 antibodies were found to associate with protection in both seasons. A titer of ≥1:40 correlated to a 44% protection in children, a 29% protection in adults 15-49years old and a 51% protection in adults 50-85years old.
    CONCLUSION:

    In 2013 and 2015, antibody titers to A/California/07/09 associated with an infection risk reduction amongst exposed household contacts. This is consistent with a detectable vaccine effectiveness reported in a number of studies. Genetic changes in clade 6B viruses might have led to a reduced immunity in some whereas others might have been less affected. The use of human serologic data is important in virus characterization and if performed in a timely manner, could assist in vaccine strain selection.
    Copyright ? 2017 Elsevier Ltd. All rights reserved.


    KEYWORDS:

    Antibody titer; Clade 6b; H1N1pdm virus; Immune correlates; Influenza

    PMID: 28986036 DOI: 10.1016/j.vaccine.2017.09.036
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